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Application of Artificial Neural Network for Prediction of the Cyclic Oxidation Behavior of Electrical Resistance Sintered Gamma-TiAl Intermetallics

Garip Yiğit, Garip Zeynep Batık, Ozdemir O.

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 2

581--591

EN

TiAl based intermetallics are widely used for structural applications in aviation, chemical engineering, automotive and sports equipment. In this study, the electrical resistance sintering (ERS) technology used in the production of gamma-TiAl intermetallics is based on the principle of applying pressure simultaneously with a high-density electric current. The purpose of this study was to investigate the cyclic oxidation resistance of Ti-44Al-3Mo and Ti-44Al-3Nb alloys (at.%) and the applicability of artificial neural network (ANN) modeling for the forecast of the oxidation behavior of these alloys. In order to obtain this aim, the alloys sintered by ERS were oxidized at 900°C for 360 h and then the oxidation behaviors of them are evaluated by plotting a graph between weight change as a function of time. The data collected after the oxidation experiments were used to construct the prediction models. The modelling results show that a good agreement between experimental results and prediction results was found. The oxidized alloys were characterized using XRD and SEM-EDS. The XRD patterns revealed the oxidation products are composed of TiO2 and Al2O3 oxides. SEM-EDS analysis indicated that the oxide scales of alloys are made up of a multilayered structure.

2

Improved flotation of heat treated lignite with saline solutions containing mono and multivalent ions

Ozdemir O., Ersoy O. F., Guven O., Turgut H., Cinar M., Çelik M. S.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 4

1070--1082

EN

Flotation of lignites is inherently difficult. However, pre-heat treatment of coal is also known to make coal surfaces more hydrophobic possibly through removal of water entrapped in the structure of coal. In this context, the objective of this study was, therefore, to determine changes in the hydrophobicity of some lignites under moderately controlled heat treatment and correlate the flotation response of lignites in different salt solutions of NaCl, KCl, CaCl2, and MgCl2 without using any reagent. The results of flotation tests suggested that under the present test conditions, it was possible to float thermally pre-treated lignite samples of partially hydrophobic character in salt solutions in the absence of collector and frother. In addition, the effect of heat treatment on hydrophobicity, and in turn flotation was explained by a theoretical model based on extended DLVO interactions to quantify the effects of both heat treatment and salt concentration on bubble-particle interactions. The results of theoretical modeling suggested that the removal of hydrogen containing groups from coal surfaces significantly contribute to the electrical double layer and hydrophobic forces that govern the magnitude of energetic barrier and also the extent of bubble-particle attachment.

3

Heterocoagulation of hydrophobized particulates by ionic surfactants

Çelik M., Ozdemir O.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 1

124--130

EN

Hydrophobic particulates, i.e. bubbles, precipitates, and coal particles are shown to exhibit similar isoelectric point (iep) values in the presence of ionic surfactants. While coal in anionic surfactant solutions exhibits negative zeta potentials in the entire pH region, coal in cationic surfactant solutions undergoes a charge reversal in alkaline pH. Adsorption and zeta potential measurements together with previously published results indicate that ionic surfactants adsorb on coal through hydrophobic bonding driven by entropy. Physicochemical similarities in the adsorption mechanisms of ionic surfactants onto the bubbles, precipitates, and coal particles are proposed to be responsible for the observed iep values and also heterocoagulation phenomena.

4

A novel technique to investigate the bubble coalescence in the presence of surfactant (MIBC) and electrolytes (NaCl and CaCl2)

Gungoren C., İslek E., Baktarhan Y., Kursun I., Ozdemir O.

Physicochemical Problems of Mineral Processing

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2018

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Vol. 54, iss. 4

1215--1222

EN

An efficiency of flotation process is strongly dependent upon the collecting ability of air bubbles. On the other hand, the liquid film formed beetween two fully or partially mobile air/liquid interfaces being in contact has low stability, which leads to fast liquid drainage. Therefore, when they approach to each other, they tend to coalescence. Therefore, bubble coalescence is usually controlled with frothers in flotation process. Meanwhile, it is known that dissolved ions inhibit bubble coalescence. In this study, the bubble coalescence in the presence of MIBC was determined using a novel technique with a modified bubble-particle attachment timer. Additionally, the effect of NaCl and CaCl2 on bubble behavior was investigated along with surface tension and bubble coalescence time aspects. As a result of study, it is seen that the bubble coalescence time can be successfully determined with a bubble-bubble coalescence timer.

5

Effects of temperature during ultrasonic conditioning in quartz-amine flotation

Gungoren C., Ozdemir O., Ozkan S. G.

Physicochemical Problems of Mineral Processing

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2017

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Vol. 53, iss. 2

687--698

EN

In this study, the effect of ultrasound on flotation recovery of quartz-amine flotation was investigated in terms of temperature influence. For this purpose, an ultrasonic probe was used for conditioning quartz surfaces in presence of dodecylamine hydrochloride (DAH), and the change in the temperature was recorded. The temperature-controlled ultrasonic conditioning tests were also carried out at various ultrasonic powers (30, 90, and 150 W) to investigate the effect of increasing temperature on the quartz-DAH flotation. The results showed that temperature of the suspension sharply increased from 23 up to 75 °C at the end of 10 min of conditioning at 150 W ultrasonic power. The flotation results for the temperature controlled and uncontrolled samples indicated that the flotation recovery increased from 45 to 65% by 90 W ultrasonic power. However, higher ultrasonic power levels affected the flotation recovery negatively. On the other hand, the ultrasonic application decreased the flotation recovery at all ultrasonic power levels in the temperature-controlled tests. Finally, the shape analysis was also performed for the particles treated with the ultrasound at various ultrasonic powers. As a conclusion, the positive effect of ultrasound on the quartz-amine flotation recovery could be related to temperature increase during conditioning.

6

Specific ion effect of chloride salts on collectorless flotation of coal

Ozdemir O.

Physicochemical Problems of Mineral Processing

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2013

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Vol. 49, iss. 2

511--524

EN

Separation of naturally hydrophobic particles, such as coal, by flotation is known to be enhanced with the addition of salt solutions into the system. In this study, the flotation of bituminous coal in the presence of NaCl, KCl, CaCl2 and MgCl2 without use of any flotation chemicals was investigated in detailed. In addition, zeta potential and foam stability tests were performed. The results from this study showed that the flotation behaviour of coal was influenced by these dissolved salts, and determined by the specific effect of these ions, while MgCl2 and KCl solutions showed the highest and the lowest flotation performance improvements, respectively. The ash content of the products also increased with the salt concentration. This can be attributed to the entrainment of the ash minerals in the salt solutions, particularly at higher salt concentrations. Meanwhile, the froth stability tests at 1 M salt concentration also indicated that there is a correlation between the flotation recovery and stability profile of the froth. These results also clearly indicated that Na+, K+, Ca2+, Mg2+ ions have a strong ion specific effect on the flotation recovery of the coal particles, and there is an optimum salt concentration to produce a clean coal in these salt solutions.